Suicide bombers killed a civilian at a beach front restaurant in a popular weekend hangout in the Somali capital on Friday, officials said.

The attack by two bombers underscored how fragile security remains in Mogadishu some 18 months after African forces and Somali government troops drove Somali militants linked to al Qaeda out of the capital.

A Somali soldier at the blast site said one civilian had been killed, as well as the bombers.

"First a suicide car bomb rammed into the gate of the restaurant and it caused no casualty. Then another blast went off when people converged," Abdiqadir Mohamed, a senior police officer, told Reuters.

A witness also reported hearing two blasts in the area.

There was no immediate claim of responsibility but the al Shabaab rebel group has vowed a campaign of guerrilla-style attacks against the new government, which is supported by Western powers and regional states.